The use of reinforcement strips or strands in conjunction with corrugated board is well known. For example, in U.S. Pat. No. 1,605,953 (Howard) unspun reinforcing fibers are adhered preferably between layers of a two ply facing sheet that is in turn adhered to corrugated paper.
Coated rayon strands are placed between the outer liner and the corrugated medium in U.S. Pat. No. 4,398,650 (Holmes et al). The coating is a thermoplastic resin material having a softening point such that it enables the strand to become adhered in place under the temperature and time conditions prevailing in the corrugating machine.
Large corrugated cartons having non-woven backing material with yarns laminated therein as reinforcement medium are disclosed in U.S. Pat. No. 4,655,366 (Sykes). Here, a belt of backing material is disposed entirely around the carton sidewalls or the tubular liner and extends upwardly for a distance from the container bottom. The belted backing material comprises a non-woven polyester with a plurality of parallel fiberglass filaments laminated therein.
U.S. Pat. Nos. 1,184,749 (Hicks) and 4,339,292 (Iton et al) are also noted as being of possible interest.
Although the prior art means of reinforcement provide strong durable container products it has been difficult to repulp same due primarily to the inclusion therein of synthetic polymer reinforcing mediums which may lead to unacceptable fiber recovery levels in the repulping process and/or "stickies" which deleteriously affect subsequent paper making processes. Stickies are impurities that can cause tears during the paper making process.
Despite the prior art efforts, there remains a need in the art to provide a strong and durable reinforcing medium for corrugated cartons and the like.
Moreover, due to ecological concerns, it is even important to provide a strong, durable reinforced corrugated container that may be repulped, providing acceptable fiber recovery during the repulping so that the corrugated container material may be recycled for subsequent use.